With the development of the broadband network and the trend of the digital technology, the wireless products with wireless transceiving functions are increasingly popular, such as a wireless network access point (AP), a mobile phone, a personal digital assistant (PDA), and a notebook computer. As a result, various functions and services are incorporated with wireless technology to provide more convenient and efficient services. But, during the wireless communication, the wireless products are sensitive to the surrounding electromagnetic waves caused by other wireless communication systems or external noises.
For example, when a wireless product performs the data wireless transmission under a high power state, the high frequency harmonic waves are extremely easily generated by non-linear characteristics of active components, so as to result in an electromagnetic interference (EMI) emission, which is often the prime contributor to the performance degradation. In order to solve the problem, legal regulations are imposed by many countries to restraint illegal input applications and utilizations of the wireless product. Accordingly, when the designers and manufactures of the wireless product design a control line of the wireless product, the legal requirements of wireless applications must be complied and incorporated into the wireless design. The circuit of the wireless product is also affected by the signals of the external electromagnetic wave, such as, radio frequency (RF) wireless signals. Therefore, performance inconsistencies can occur easily in the wireless products.
Therefore, it is a critical factor for the designers and developers to know how to effectively eliminate the interference and the noise in order to improve the performance of the wireless products. One of conventional methods is to use an isolation cover disposed on a circuit board to eliminate the interference. As shown in FIG. 1, an isolation cover 22 is fully soldered onto a main body 20 of a circuit board 2 by adopting a surface mount technology (SMT), such that the isolation cover 22 can cover part of components on the circuit board 2, such as, the chip(s) located on a surface of the main body 20 of the circuit board 2. Then, a reflow-soldering process is performed on the circuit board 2 through a tin oven (not shown).
However, this conventional method is used a soldering technique called a single piece fully soldering process to solder the isolation cover 22 entirely onto the circuit board main body 20. After the reflow-soldering process, if some of the components underneath the isolation cover 22 fail, a desoldering process must be performed to detach the isolation cover 22in order to replace the corresponding components. In this manner, the maintenance is costly, and the repairing process is time consuming, and the surface of the main body 20 of the circuit board 2 can be easily damaged or deformed, more significantly, the detached isolation cover 22 cannot be reused. As a result, the fabrication cost of the conventional method is extremely high.
In order to solve the disadvantage of the single piece fully soldering technology, a two-piece fully soldering technology is proposed, as shown in FIG. 2. A lower frame 24 and an upper cover 26 are used to replace the single piece isolation cover. During assembling, the lower frame 24 is firstly soldered to the main body 20 of a circuit board 2′. The upper cover 26 is utilized to cover the main body 20 of the circuit board 2′ after the circuit board 2′ passing through the tin oven, in such that the upper cover 26 can be integrated to the lower frame 24.
However, the requirements of performing the two-piece fully soldering process are more complicated, and the cost is relatively higher. At the same time, both the single piece fully soldering technology and the two-piece fully soldering technology require the solder tin to perform the soldering process, and the heat dissipation is the major problem during the soldering process which can severely damage to the components on the circuit board and the circuit board itself.,
Some conventional methods are proposed to resolve the above-mentioned problems, such as the methods disclosed in PRC Utility Model Patent Publication No. CN201063966Y, and US Patent Publication Application No. 2008/0043453 A1. In the PRC Utility Model Patent Publication No. CN201063966Y, the isolation cover is used to cover the entire circuit board, and an elastic arm with an inward end is designed to clamp the periphery of the circuit board. In the US Patent Publication Application No. 2008/0043453 A1, the surface of the partial circuit board is covered by the isolation cover passing through the circuit board, and an interfering structure with an outward end is designed to fix the isolation cover on the circuit board.
In both teachings, solder tin is not an essential requirement to perform the soldering process. However, the elastic arm or the interfering structure is easily deformed by the high temperature resulted in the subsequent process, thereby affecting the buckling force to cause the falling of the isolation cover.
From the above-mentioned methods, the conventional methods have many problems, therefore, it is an objective of the present invention to provide a true solution to those drawbacks, and an improved circuit board of a communication product and a fabrication method that can successfully eliminate the interferences.